Lens



Search Room Patented Dec. 7, 1943 LENS Willy Schade, RochesterQN. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application September 17, 1941, Serial No. 411,181

6 Claims.

This invention relates to lens systems and particularly to high aperture photographic objecand the curvature of its rear surface being numerically greater than tives.

An object of this invention is to provide a photographic objective with an aperture greater than 5 F f/3.0, covering a large field with an angle of about and less than 25 or more from the axis, more economical to 2.5 manufacture, and with better corrections of zonal I "T aberrations and oblique spherical aberration than v heretofore, The third airspace is greater than 1.5 times and In the development of high aperture photoless than 10 times the sum of the first two airgraphic objectives an important step was the spaces. The indices of all the po itive lements splitting of the front component of th C ok are above 1.57 and the indices of the first and triplet type into two'positive components at least ird mp n s differ y l han 5- These the second of which counting from the front of at s re all r o nized by s d s ners as the objective is meniscus in shape and convex tonging to and being more or less distinctive of ward the front. This step resulted in a decidedly e type of objective in q esti n- Of course comnew type of objective which has developed into a p nding of the various components has been number of forms, in some of which all four comtried f r Various p poses such as pur f ponents con i t of simple l n hil i others achromatization with various degrees of success. one or more of the components is compounded. According to t p t i v n n a lens f Even with the simple components, the zonal aberthis g r l ype includes a second component rations were so reduced as to constitute a notable which is cflhstructed f a ne a ve el ment oeadvance over previously k wn th or fgur mented onto the front of a positive element of component objectives and to make possible about higher index, he index difference being greater twice the speed with equal covering power. than The upper hmlt of 151115 index Generaily the best results in regard to the corence 1S deiiermmed by the range of avallable rection of the usual first order aberrations and glasses and 1s abou? or I the zonal aberrations have been obtained in ob- This 15 espefciauy favorable for jectives of this type by the following features. so duqing h obhque Sphenca] abenfation and zonal The front surface has a radius of curvature beestlgmatlsm and resulots in supenor sharpness of tween 0.3 F and F where F is the focal length of t? the axis- It is the objective. The focal length of the second uable m obJecf'wes m Whlch the other three component is between /3 and 3 times the focal pqnents are slmple lenses but may be combmed length of the first component. The third com- Wlth Structurem the opher compo ponent is biconcave as in the Cooke triplet and gggia fi i 12: 2: 32 53 2} 3 3 3 2 its front surface has a radius of curvature be- In an Objective t g i th tween two and ten times that of its rear surface. focal len th of the S c 0 y t is e The fourth component is sometimes simple and b1 t d t th e on cfompongn 2 wmetimes including a negative :he f oZZI I eSgth Of h e n rgt iiiganifit in??? ment cemented Onto the front of higher index dius of curvature of its front surface is prefer positive element. It is either biconvex or weakly ably longer than that of the front surfac of th meniscus the curvature of its front surface being e first component, and the front positive component algebraically between minus 3 is meniscus in shape.

05 In a preferred form of the invention the power T of the cemented surface in the second component and plus is greater than and the first and third components are simple lens elements.

In my U. S. Patent 2,259,004, a similar structure of the second component is shown combined with a triplet rear component. According to the present invention, however, the break in index at the cemented surface is greater and according to the preferred forms the power of this surface is considerably greater than the radius of curvature of the front surface of this component is longer. These features combine favorably with the simpler rear component to control the Petzval sum and the zonal astigmatism. The simpler structure of the rear component, of course, re-

sults in lower manufacturing costs.

In the accompanying drawing:

Fig. 1 shows an objective according to the invention;

Fig. 2 shows the constructional data for one embodiment.

The constructional data are as follows:

This embodiment has all the features of the preferred form of the invention. The second component is meniscus in shape and made of a negative element cemented to the front of a positive element with index higher by 0.127 than the negative element, the cemented surface having a power of The focal length of the second component is 1.8 times the focal length of the first. The other features are readily apparent from the above table of data.

Iclaim:

1. A high aperture photographic objective comprising four air-spaced components in the following order, a front positive component, a meniscus positive component convex toward the front, a biconcave component, and a rear positive component, the latter two components being separated by a distance between 1.5 and times the sum of the other two airspaces between the first three components, the front surface of the front positive component being convex with a radius of curvature between 0.31 and F where F is the focal length of the objective, the meniscus positive component consisting of a negative element cemented to the front of a positive element and having a focal length between onethird and three times the focal length of the front positive component, the positive element ofthe meniscus positive component having an index of refraction greater than that of the negative element by more than 0.08, the front surface of the biconcave component having a radius of curvature greater than twice but not greater than ten times the radius of curvature of the rear surface of the same component, and the rear component having for its front surface a curvature algebraicly between minus 0.5/F and plus 1.6/F' and for its rear surface a curvature between minus 1.0/F and minus 25/1. I

2. An objective according to claim 1 in which the radius of curvature of the front surface of the meniscus positive component is between one and five times the radius of curvature of the front surface of the front positive component and the focal length of the meniscus positive component is between 0.8 and 2.8 times that of the front positive component.

3. A high aperture photographic objective consisting of four air spaced components, the first component being a meniscus positive element with refractive index between 1.58 and 1.64, the

second component being a meniscus positive doublet concave toward the rear consisting of a a negative element cemented to the front of a higher index positive element and having a focal length between 0.8 and 2.8 times the focal length of the first component, the third component being a biconcave element with refractive index difiering from that of the first component by less than 0.05 and having the radius of curvature of its front surface between two times and ten times the radius of curvature of its rear surface, and the fourth component being a bicon-' vex doublet consisting of a negative element cemented to the front of a higher index positive element, and the distance from the third to the fourth component being greater than the sum in F and the index difference at this cemented surface being greater than 0.08.

4. A photographic objective having substantially the following specifications:

where the first column gives the lens elements in roman numerals in order from front to rear'and indicates air spaces by dashes and where f is the focal length of the objective, No is the index of refraction for the D line of the spectrum, V

is the dispersive index, R, t and S refer respecfrom the front, and the and signs in the 1 fourth column correspond to surfaces which are respectively convex and concave to the front.

5. A high aperture photographic objective comprising four airspaced components in the following order, a front positive component, a me- Search Room niscus positive component convex toward the front, a biconcave component, and a rear positive component, characterized by the meniscus positive component being compound with a positive element having an index of refraction greater than 1.7 cemented to the rear of a, negative element whose index of refraction is at least .08 less than that of said positive element.

6. A high aperture photographic objective comprising a single meniscus positive element con,- vex to the front as its front component, a compound positive rear component and between said front and rear components a member including at least two negative elements and at least one positive element, one oi! the negative elements being at the rear of the member, said at least one positive element having an index of refraction greater than 1.7 and being cemented to the other oi. said negative elements which other of said negative elements has a refractive index at least .08 less than that of said one positive ele- 10 ment.

, WILLY SCHADE.

CERTIFICATE OF CORRECTION. I Patent No. 2,556,500. December 7, 19).;5.

WILLY SCHADE.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows; Page 2, first column, line 9, for "greater than" read "greater and--; and that the said Letters Patent should be read with this correction therein that the same may conform to the record oi-the case in the Patent Office.

Signed and sealed this Ijth'day of Febmary, A. D. 191m.

4 Henry Van Arsdsle, (Seal) 4 Acting Commissioner of Patents. 

